Having a heavier college roommate may mean you won't gain that much weight

Peers can influence our behavior in positive and negative ways. A new study finds that female college freshmen who room with heavier women may gain less weight.

The study focused on 144 female college students who were randomly assigned roommates at the start of freshman year. They were asked their height and weight as well as what, if any, weight management activities they were involved with, such as being on a diet, exercising and using weight loss supplements.

Researchers found that study participants who roomed with women who weighed more than average actually gained less weight during their freshman year than women who roomed with more slender gals. The difference was an average half-pound weight gain compared with an average 2.5-pound weight gain.

"It's not really the weight of your roommate that's important, but the behaviors your roommate engages in," said study co-author Kandice Kapinos of the University of Michigan in a news release. "These behaviors are what may really be 'contagious.' "

Kapinos added that heavier freshman may be more apt to diet than women who are of average weight. They may also exercise more often and be more prone to using weight loss supplements.

Another study published by the New England Journal of Medicine in 2007 found that obesity may be socially contagious among family and friends. One person's chances of becoming obese went by up significantly if they had a friend, sibling or spouse who became obese.

Arbitrary roommate relationships may be key. "These relationships [in the NEJM study] are obviously not random," Kapinos added. "People pick their friends and spouses, and they often select people who are similar to themselves. And even though we don't pick our siblings, we share a genetic inheritance and an early environment that may influence adult weight."